The Seattle U.S. Public Health Service Hospital has recently begun routine production of computerized drug profiles for an 80% sample of its clinic patients. With each change in a patient's regimen, and update summary of the patient's current and past medications is produced and becomes part of the permanent medical record. On subsequent visits, providers can make most changes to the regimen by writing directly on the profile. Because the profile enhances the accessibility of patient-specific drug information to providers, it is expected to improve prescribing by facilitating detection of potentially significant drug interactions and redundancies. It should also reduce provider time spent on reviewing the chart, documenting the therapeutic regimen, and writing prescriptions. Better syncrhonization of refills should save patient time by necessitating fewer visits to the pharmacy. The major incremental costs are computer operating costs and medical record clerk filing time. The proposed project would evaluate the extent to which the expected benefits of profiles are achieved and would quantify operation costs of the system. Baseline data were collected for five months before introducing profiles, and they have since been implemented for an 80% random sample of clinic patients. Hence a pre-test post-test randomized control group design is proposed, using the computerized data base and observation data from a sample of provider-patient encounter. The findings should be relevant to many sites at which such profiles could be introduced at low cost.